The present invention relates in general to semiconductor devices and, more particularly, to high current semiconductor devices for limiting current surges on a power supply bus.
Telecommunications, network and computer applications often require the ability to insert and remove circuit cards from systems without powering down the entire system, often referred to as “hot swapping”. In network equipment configured with a distributed power system, circuit cards often include large filter capacitors for reducing noise on the power rail or bus. During a hot swap, the capacitors can produce an inrush current spike that can, if not otherwise limited, reach hundreds of amperes of peak amplitude, which can damage the circuit card or its connector. Moreover, such a large inrush current can cause a power disturbance that damages other circuit cards that are plugged into the system or result in a data loss or other system malfunction. To prevent such deleterious effects, hot swappable circuit cards typically are formed with inrush current limiting circuits that control a power MOSFET switch through which is routed the supply current.
Existing inrush current limiters suffer from a high cost due to a large number of components needed to control the power MOSFET switch in a fashion that achieves a limits the inrush current to a specified level. Most inrush current limiters use a low value sense resistor coupled in series with the power MOSFET switch to limit the peak value of the supply current. However, a large current flow through the switch and sense resistor results in a high power dissipation that can adversely affect reliability.
Hence, there is a need for an inrush current limiter that reduces the component count in order to reduce the manufacturing cost while achieving a high reliability by reducing power dissipation.